(a) The present invention relates to a plate type condenser comprising a plurality of heat transmitting plates assembled face to face to form therebetween alternate passages for steam and the cooling liquid so that the steam condenses as a result of heat transmission between the steam and the cooling liquid.
(b) In improving the heat transmitting ability of such kind of a condenser, what becomes a problem is "film coefficient", which is defined as the heat conductivity of the film divided by the thickness of the film and varies with the condition of the heat transmitting surface, i.e. it is decided by adhering conditions of condensate onto the heat transmitting surface.
As condensation continues to occur, this film becomes gradually thicker and eventually flows down along the vertical heat transmitting surface under its own weight until a thick layer of downflow liquid is formed in the lower region of the heat transmitting surface substantially throughout its width. This downflow liquid layer becomes gradually thicker towards in the downstream direction and the heat transmitting surface covered with steam hence the film coefficient in this region is decreased, badly lowering the heat transmitting ability. Therefore, in order to improve the heat transmitting ability on the entire heat transmitting surface on which steam condenses, it is necessary to take measures capable of preventing the filmy downflow liquid layer from its growth in thickness as well as wideness.
To this end, the applicant's U.S. Patent Application Serial No. 750,909, filed December 15, 1976, discloses a condenser having heat transmitting surface whose condensate discharging effect is high. (refer Ser. No. 750,909 filed on Dec. 15, 1976) In this condenser, as shown in FIGS. 1-3 each of which illustrates the prior art, heat transmitting plates 1 and 7, which are assembled face to face so that steam passages A and cooling liquid passage B formed alternately therebetween, are provided with a condensate collecting and discharging means consisting of inclined grooves 2, 8 and vertical grooves 3, 9 and further provided with a plurality of longitudinal grooves (not shown in FIG. 1) in the form of a series of ridge parts 4, 10 and valley parts 5, 11 in section (when seen from the steam passage A side) extending in the direction of the stream of steam between the inclined grooves and communicating with one of the inclined grooves at their lower ends.
Condensate successively occurring on the heat transmitting and condensing surface is, as indicated with the chain line in FIG. 3, attracted into the valley parts 5, 11 under the action of surface tension, and flows down the valley parts under the influence of gravity toward the inclined grooves 2, 8. As a result, the film coefficient on the heat transmitting surface will be kept high and the heat transmitting ability will be improved, since no downflow liquid is formed on the ridge parts 4, 10.
However, even in the above described arrangement, condensate is liable to flood out of the inclined grooves and to flow down onto the lower region of the heat transmitting surface, for condensate flows down with large inertia force as its velocity increases. In this lower region, thus the liquid layer grows again, lowering the heat transmitting ability. Moreover, even if thermodynamically suitable heat transmitting ability is accomplished through the above described measures, there still remains a problem from the view point of hydrodynamics. If the amount of the cooling liquid supply is deficient due to, for example, a certain disadvantage in the construction of the cooling liquid passage, thermal polution or the like is brought about by the pyrogenic liquid exhausted out of the system because of the fact that mean temperature difference between the steam side and the cooling liquid side extremely decreases, in other words, temperature in the exhausted cooling liquid reaches to the last degree.
Such problem may be dissolved readily by supplying a large flow of cooling liquid, however, the amount of the cooling liquid supply is limited in accordance with the clearance of the cooling liquid passage so that the pressure loss does not increase. This clearance between the heat transmitting plates, which are maintained in a fixed distance by means of a plurality of hemispherical projections formed in the transmitting plate through the press work, is in turn limited in accordance with the height of the projections, and is not able to be extended over a given extent, since the height of the projections is limited within a possible range of the drawing ratio in the press work.
The steam passage is under the same circumstance that the passage clearance is limited within a fixed distance. Therefore, the pressure loss as well as the velocity of steam increases and condensate collected in and flowing down the inclined grooves is liable to scatter and to adhere onto the lower region of the heat transmitting surface. In addition, the number of the projections to be arranged on the heat transmitting plate is necessarily limited to a lesser extent so that the sectional area of the steam passage is not decreased due to the existence of the projections, and this means the reduction of mechanical strength for maintaining the passage clearance in a fixed distance.